Mechanism of controlled thermal injury

The Pelleve procedure, performed using the 4.0 S5 Surgitron (Ellman International, Oceanside, NY, USA), differs from other methods of delivering RF energy because it delivers a progressive but controlled thermal injury to the dermis and subdermis and overcomes many of the shortcomings associated with pulsed and fixed dosed methods.

A 4.0-MHz high-frequency energy is used, so the difference in resistance between the dermal skin and underlying fat is maximal and results in heat generation and diffusion only from the dermal-subdermal junction. The energy delivery is continuous, but because of the constant movement of the electrode over the treatment area, heating is gradual, rather than sudden, allowing the procedure to be painless but thorough when performed properly. A dispersion gel is used on the skin to allow smooth movement of the electrode and immediate dispersion of the energy of the otherwise-focused flow of electrons. Because all the heat generated emanates from deep at the dermal-subdermal junction as seen on infrared images ( Fig. 3 ), no direct surface cooling is required and potentially beneficial effects to the middle and upper dermis are not compromised. In addition, because the heat conducted down connective tissue bands is also gradual and progressive, it has been demonstrated that the fat compartments are contracted, giving 3-dimensional deep tissue contraction without the fat cells reaching temperatures that could cause atrophy or necrosis.

Sagittal infrared imaging of monopolar heating from the dermal-subdermal junction.

This process has been demonstrated in vivo ( Fig. 4 ). With progressive heating, the “cloud” of thermal energy rises up into the dermis and down the connective bands. Temperature levels at the surface have been documented to be approximately 20° cooler than those at the dermal-subdermal junction as seen in Fig. 3 .

Infrared images: in vivo abdominal flap.

The optimal threshold temperatures at, and adjacent to, the dermal-subdermal junction can be reached repeatedly in a controlled manner by monitoring the surface temperature and staying aware of the patient’s pain response, which correlates nicely with temperature levels and seems to be consistent from patient to patient.

It has been shown with the Thermage device (Solta Medical, Hayward, CA, USA) that multiple passes at lower energy levels produce more collagen contraction and new collagen production than single passes at higher energy levels.

With the gradual heating characteristic of the Pelleve procedure, the patient’s response to a threshold temperature of 40°C to 45°C at the surface correlates with a heat sensation of “just getting hot” or a heat perception level of 7 to 8 out of 10. An infrared surface temperature monitor can be used in addition to the patient’s feedback so that repeated passes can be preformed to the therapeutic threshold until clinically significant smoothing or tightening is seen in every patient without pain or unforeseeable jumps in temperature to dangerous levels. This subjective goal of repeating passes to threshold temperature until no additional contraction or smoothing is seen in each treatment session can be objectively stated to be 1 pass per decade of age plus or minus one pass depending on the anatomic area and the skin’s age and condition. In the case of the Pelleve procedure, a pass is defined as reaching threshold temperature confluently over the entire section being treated, not just covering the area with the probe passing over it, followed by forced cooling for 10 to 20 seconds. This procedure may take 30 seconds to a minute or more of persistently going over an area to bring it to the threshold temperature depending on energy output settings, the speed of the operator’s hand movement, and how much area is being treated at once. With experience, higher settings can be used comfortably and passes can be completed more efficiently, which reduces the overall treatment time. So again, a pass is defined as bringing the selected treatment area, that is, half the forehead, cheek, and periocular area, confluently to a threshold temperature of 40°C to 45°C and then cooling for 10 to 20 seconds, maximal 3-dimensional contraction is desired. One pass per decade of age plus or minus one pass in each area seems to be the amount of treatment in a given session to achieve clinically reliable and lasting results. One to 3 sessions may be required to achieve the desired degree of improvement that depends on multiple factors. These factors include age, degree of collagen loss, degree of volume loss, stage of volume loss, and genetic factors. Therefore, a session, single complete procedure, is the completion of the appropriate number of passes to all planned treatment areas. Clinically, it seems that each additional pass generates progressively greater contraction to a point to which no further benefit is seen or palpated, and this technique is what yields predictable results painlessly.

Cooling controversy

After several months’ experience, using multiple passes from 40°C to 45°C, going on to an adjacent area to allow spontaneous cooling of the treated area, and then returning to the treatment area, the possibility that the progressive swelling occurring with each pass might overcome the ability for acute tissue contraction became apparent. At that time, I began cooling the treated area directly with frozen reusable cold packs to force contraction of the solid proteins that were being heated and, at the same time, minimized the acute swelling associated with repeated heating. The immediate contraction and firming of the treated area was apparent, and it allowed repeated passes of continuing RF energy on the same areas until maximal contraction was seen without having to go to adjacent areas to allow passive cooling to occur. After only 20 to 30 seconds of cooling, the subsequent passes seemed to trigger an even more significant contraction without the swelling seen when letting the tissue cool passively. The distance between a point on the nasolabial fold and the tragus, for instance, increases after a pass of heat solely but decreases after a pass followed by cooling. The principle of physics governing cooling solids is that all solids, except water, contract with cooling. If application of cold causes even a fraction of a millimeter of additional contraction of the denatured collagen, then each subsequent pass would reach that much deeper and cause greater contraction and increase the density of the layers of deep dermal collagen. This occurrence is apparent on pinching the skin after each pass of hot and cold application.

Some investigators have suggested that heat shock proteins triggered by the injury could be adversely affected. It was shown that only cooling at or less than 5°C adversely affected the tissue’s response to injury, and cooling to that level is not advocated here.

To document what I have observed over the past several years, 10 consecutive patients were treated with one side heated to threshold temperature and then cooled for 30 seconds using an iced stainless steel roller and the other side of the face heated to threshold but left to cool passively while an adjacent area was treated. The midface was treated at a setting of 80 for 5 passes; the forced cooling for 30 seconds reduced the temperature to 20°C to 24°C. The opposite midface was treated at the same level for 5 passes but allowed to come to baseline temperature of approximately 33°C passively while an adjacent area was treated. The acute evaluation at the end of the treatment session and an evaluation 1 month later revealed significantly more contraction and lift on the side with cold applied for forced contraction at both end points. All 10 patients felt that the side with cold applied for forced contraction felt tighter at rest and felt denser when pinched relative to the passively cooled side. All patients were then treated the opposite way, and, at the end of the second month, all felt equally tight. The acute response at the end session was the same, the cooled side felt tighter and denser. All 10 patients also felt that the 2 treatments gave significant firmness and tightening to their skin, greater with the second treatment, and each could see an obvious contraction through the midface relative to their pretreatment photos.

Cooling controversy

After several months’ experience, using multiple passes from 40°C to 45°C, going on to an adjacent area to allow spontaneous cooling of the treated area, and then returning to the treatment area, the possibility that the progressive swelling occurring with each pass might overcome the ability for acute tissue contraction became apparent. At that time, I began cooling the treated area directly with frozen reusable cold packs to force contraction of the solid proteins that were being heated and, at the same time, minimized the acute swelling associated with repeated heating. The immediate contraction and firming of the treated area was apparent, and it allowed repeated passes of continuing RF energy on the same areas until maximal contraction was seen without having to go to adjacent areas to allow passive cooling to occur. After only 20 to 30 seconds of cooling, the subsequent passes seemed to trigger an even more significant contraction without the swelling seen when letting the tissue cool passively. The distance between a point on the nasolabial fold and the tragus, for instance, increases after a pass of heat solely but decreases after a pass followed by cooling. The principle of physics governing cooling solids is that all solids, except water, contract with cooling. If application of cold causes even a fraction of a millimeter of additional contraction of the denatured collagen, then each subsequent pass would reach that much deeper and cause greater contraction and increase the density of the layers of deep dermal collagen. This occurrence is apparent on pinching the skin after each pass of hot and cold application.

Some investigators have suggested that heat shock proteins triggered by the injury could be adversely affected. It was shown that only cooling at or less than 5°C adversely affected the tissue’s response to injury, and cooling to that level is not advocated here.

To document what I have observed over the past several years, 10 consecutive patients were treated with one side heated to threshold temperature and then cooled for 30 seconds using an iced stainless steel roller and the other side of the face heated to threshold but left to cool passively while an adjacent area was treated. The midface was treated at a setting of 80 for 5 passes; the forced cooling for 30 seconds reduced the temperature to 20°C to 24°C. The opposite midface was treated at the same level for 5 passes but allowed to come to baseline temperature of approximately 33°C passively while an adjacent area was treated. The acute evaluation at the end of the treatment session and an evaluation 1 month later revealed significantly more contraction and lift on the side with cold applied for forced contraction at both end points. All 10 patients felt that the side with cold applied for forced contraction felt tighter at rest and felt denser when pinched relative to the passively cooled side. All patients were then treated the opposite way, and, at the end of the second month, all felt equally tight. The acute response at the end session was the same, the cooled side felt tighter and denser. All 10 patients also felt that the 2 treatments gave significant firmness and tightening to their skin, greater with the second treatment, and each could see an obvious contraction through the midface relative to their pretreatment photos.